A typical robot system is made of one controller, at least one sensor and at least one actuator. The sensor is read by the controller and the value of the sensor is used by the controller to compute a new value to write in the actuator. The sensor is used to capture physical properties around a zone of interest. The physical properties can be temperature, pressure and even images. The sensor is responsible to convert the physical properties into digital values and send this sensor information to the controller. The actuator is a motor used to control a mechanism and change the physical environment. The actuators are controlled by the robot controller typically to move the robot arms. An example of such system is detailed in FIG. 1 below.
The communication between the robot controller and the sensors can be advantageously implemented by wireless communication. The main advantage of wireless communication is to save cost regarding the wiring of the robot frame. The wireless communication can be advantageously implemented by using the 60 Ghz frequency band allowing to achieve multi gigabit throughput hence allowing very low latency high resolution image transfer. The scheduled protocols for wireless channel access control are best suited for the robot wireless communication implementation. Only these protocols can guaranty channel access timing which is the very basis of any real time higher level protocol. Image sensor control must be implemented by higher level real time protocols. The scheduled protocols, like TDMA (Time Division Multiple Access) for example, set a master node in charge of defining access time slots for all the nodes and it includes mechanisms for any node to claim and release access to the time slots. The master is in charge of managing wireless transmission time slots. Slaves cannot send wireless frames unless previously instructed by the master to do so.
These systems are real time systems where the latency between the moment when the controller asks for information from a sensor and the moment it receives the sensor information should be kept as short as possible.
The communication being wireless, as in all wireless transmission system, the available bandwidth is always a valuable resource. In consequence, especially in the case where the size of the sensor information is important as, for example, for image capture sensors, the bandwidth consumption of the transmission should also be kept as small as possible.
The problem is therefore to determine a scheduled transmission protocol for the command and the transmission of sensor data under these two constraints.
The present invention has been devised to address one or more of the foregoing concerns.